The present invention relates generally to angular position sensors.
Electrical generators (also referred to as xe2x80x9calternatorsxe2x80x9d) are standard equipment on motor vehicles. In a typical motor vehicle, a generator is mechanically coupled to an engine crank shaft, e.g., by a first pulley mounted on the crank shaft, a second pulley mounted on a shaft within the rotor of the generator, and a belt disposed around both pulleys. As the crank shaft rotates, the generator rotates and creates current which is used to power the electric components within the vehicle.
The present invention recognizes that it is sometimes necessary to know the angular position of the generator shaft. It happens that the angular position can be determined using a sensor assembly that includes multiple magnets that are precisely affixed to the end of the generator shaft and multiple magnetic field sensors placed in proximity to the magnets. Accordingly, the position of the magnets and, hence, the position of the generator shaft, can be determined. Unfortunately, the need for multiple magnets and the precision in which they must be installed on the shaft, increases the cost of the sensor assembly.
As such, the present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
An angular position sensor assembly for a motor vehicle generator shaft includes a housing and one magnet placed within the housing. Plural magnetic field sensors are disposed within the housing such that they are within a magnetic field created by the magnet. The sensors are placed near the end of a generator shaft that is alternatingly formed with plural slots and plural teeth. Accordingly, the sensors sense changes in the magnet field caused by the slots and teeth as they pass by the sensors.
In a preferred embodiment, the end of the shaft is formed with six slots and six teeth. Moreover, the slots and teeth are equally sized and shaped and equally spaced around the outer periphery of the end of the shaft. Preferably, the sensors are disposed on a circuit board that is placed parallel to the end of the shaft. In a preferred embodiment, the plural sensors include a first sensor that is disposed on the circuit board, a second sensor that is disposed on the circuit board so that it is one hundred and forty degrees from the first sensor, and a third sensor that is disposed on the circuit board so that it is one hundred and forty degrees from the second sensor. As such, an electrical signal from the second sensor is twenty degrees out of phase with an electrical signal from the first sensor and an electrical signal from the third sensor is twenty degrees out of phase with the electrical signal from the second sensor. A microprocessor is connected to the sensors and receives signals from the sensors that represent the angular position of the generator shaft. Preferably, the sensors are Hall effect sensors.
In another aspect of the present invention, a motor vehicle system includes a generator that has a rotating shaft. The shaft includes an end that is alternatingly formed with plural slots and plural teeth. An angular position sensor assembly is affixed to the generator in proximity to an end of the shaft. The sensor assembly includes a housing that has one magnet and plural magnetic field sensors placed therein. In this aspect of the present invention, the sensors are placed within the housing such that they are proximal to the end of the shaft. Accordingly, the sensors sense changes in a magnet field caused by the slots and teeth as they pass by the sensors when the shaft rotates. A microprocessor is connected to the sensors and receives signals from the sensors that representing the angular position of the generator shaft.
In yet another aspect of the present invention, an angular position sensor assembly includes a target wheel that is alternatingly formed with plural slots and teeth. The sensor assembly also includes one magnet and a first, second, and third magnetic field sensor placed in the same plane. The sensors are placed between the magnet and the target wheel. Moreover, the sensors are configured so that a signal from the second sensor is out of phase with a signal from the first sensor and a signal from a third sensor is out of phase with the signals from the first and second sensors.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: